Apparatus for blocking optical lens blanks



March 22, 1949.- F, G, FH ZSCHE 2,465,153

APPARATUS FOR BLOCKING OPTICAL LENS BLANKS Filed March 24, 1947 65 r- I,W 63 69 [NVENTOR n; i flew 6. FE/TZSCHE Patented Mar. 22, 1949 OFFICEAPPARATUS FOR BLOCKING OPTICAL LENS BLANKS Fred G. Fritzsche, Milwaukee,Wis.

Application March 24, 1947, Serial No. 736,663

The present invention relates in general to improvements in the art ofblocking lens blanks preparatory to final grinding of the lenses, andrelates more specifically to improved apparatus fr mounting optical lensblanks upon supports to firmly hold the blanks while subsequent grindingis being effected.

Theprincipal object of this invention is to provide an improved systemfor blocking lens blanks in order to insure greatest possible accuracyin subsequent grinding of the blanks and polishing of the lenses.

It has heretofore been customary in the manufacture of optical lenses,to initially produce standard lens blanks with final convex curvature onone side and with arbitrary concave curvature on the opposite sidethereof. Whenever one of these standard blanks was to be ground, it wasblocked or attached to a recessed circular holding block with the aid ofa layer of pitch interposed between the convex surface of the blank andthe block recess, and with the blank in contact with the sharpperipheral edge of the block surrounding the recess. In accordance withprevious commercial practice, each mounting block was placed upon ahorizontal support with its cup-shaped recess upwardly exposed, afterwhich the recess was filled with hot fluent pitch and the convex face ofthe lens blank was applied to the molten pitch and pressed downwardlyuntil the blank contacted the peripheral ridge of the blank, the blankbeing held thus until the pitch hardened. The excess fiuent pitch wasexpelled from the recess during the pressing operation throughdiametrically opposite transverse slits formed in the peripheral ridgeof the block, and would run down the adjacent sides of the mountingblock; and this excess material was scraped oil after the pitch confinedwithin the recess had hardened sufllciently to hold the lens blank inplace.

This mode of removing excess pitch was not only extremely messy andwasteful. but it would also permit air pockets to form within the pitchladen recesses of the mounting blocks, and this entrapped air wouldfrequently diminish the holding eifect of the hardened pitchto such anextent that the lens blanks would fall oil? or become loose during thegrinding operation. Then too, it often happened that the workmen wouldnot press the lens'blanks solidly against all portions of the blockridges, thus resulting in the production of imperfect and inaccuratefinal lenses. has been found that actual contact between the In additionto these dimculties, it-

7 Claims. (Cl. 51-277) lens blanks and the mounting blocks along themetallic peripheral ridges of the latter, diminishes the bonding orholding effect of the pitch bed which shrinks slightly upon cooling andtends to tear away from the convex lens surface due to the metal toglass contact near the periphery of the blank; and that far moreeifective mounting results if the pitch is caused to contact the blanksalong maximum available surface and as near to the peripheries thereofas possible.

It is therefore a more specific object of my invention to provide a modeof fastening lens blanks to carrier blocks with the aid of pitch or thelike, which definitely eliminates the prior waste and messy conditionsand which enables convenient, firm and accurate mounting of the blanksupon the blocks.

A further specific object of this invention is to provide an improvedapparatus for more firmly and accurately attaching optical lens blanksto mounting blocks with the aid of pitch and preparatory to finalgrinding and finishing, in an expeditious manner.

Still another specific object ofmy present in-- vention is to provide amode of effecting firm attachment'of lens blanks to carrier blocks, by

is to provide apparatus for utilizing maximum available contact areabetween the lens blank and the bed of pitch for attaching the blank to amounting block, thus insuring more durable and reliable attachment thanhas heretofore been possible with prior lens blocking methods.

These and other objects and advantages of the present improvement willbe apparent from the following detailed description.

A clear conception of the features involved,-

and of the construction and operation of typical mechanism for carryingon commercial exploita- Fig. 3 is a part sectional enlarged and moreaccurately illustrated side elevation of one of my improved mountingblock and supporting assemblages, showing the position assumed by a lensblank while being attached to the block;

Fig. 4 is a likewise enlarged top view of the assemblage shown in Fig.3;

Fig. 5 is a fragmentary part section side view of the pump plungeractuating handle, showing details of construction of the guide and lockfor this handle;

Fig. 6 is a fragmentary side elevation of the pivotal end mounting ofthe lens blank holdin arm, the view being taken looking toward the leftin Fig. 1; and

Fig. 7 is a sectional view of the pitch shutoff valve associated withthe pivot stem of the lens blank holding arm,

Although the invention has been shown and described as being especiallyadvantageously applicable for blocking optical lens blanks preparatoryto grinding and polishing thereof, it is not my intention tounnecessarily restrict the utility of the improved apparatus by virtueof this limited disclosure.

Referring to the drawing, the ordinary or standard optical lens blanks'9are usually formed of glass and are of substantially uniform thicknessand various diameters, bein provided on one side with a convexly curvedfinal surface or face In of definite curvature, and on the opposite sidewith a concave surface orface l l of arbitrary curvature and which isordinarily approximately parallel to the surface l0, see Figs. 1, 2 and4. Depending upon whether the blanks 9 are to be used for the productionof ordinary or bi-focal final lenses, each standard blank is providedwith a pair of hair lines [2 on the concave face ll thereof.intersecting either at the true geometrical center, or at an eccentricpoint of the cylindrical blank. These stock lenses are furnished by themanufacturers in large quantities and various sizes, and must beaccurately ground and finished along their concave surfaces II to meetvarious specifications and prescriptions, whereupon they are shaped tofit the final supporting frames or rims.

In order to facilitate grinding of the concave faces II of the lensblanks 9, each blank must be firmly attached to a metal mounting block Hof cylindrical formation having an upper cavity or recess l5 thereinsurrounded by a peripheral ridge [6 provided with diametrically oppositeslits or notches l1, and the bottom of each of these standard mountingblocks I4 is bounded by a fiat surface [8. The upper block recess I5 isbounded by an approximately spherical surface generated with a shorterradius than that of the convex lens blank surface I ll, so that when ablank 9 is disposed with its surface l0 facing the recess l5 andcontacting the ridge IS, the blank will not contact the recess bottomand considerable space is left between the blank and the bottom of therecess I5 for the reception of pitch. The four notches I! in the ridgel6 of each block M are spaced ninety degrees apart and serve as markerscooperable with the intersecting hair lines l2 of the blanks 9 toproperly position the latter upon the blocks l4 preparatory to grinding.

All of the foregoing details of construction of the mounting blocks iiare old and well known,

and as previously indicated, it was heretofore customary to completelyfill the recess l5 of each individual mounting block [4 while restingupon its bottom surface IS with hot molten pitch 20 4 and to thereafterapply the convex face ll of the blank 9 to be attached, to the recess l5and to press the blank into firm contact with the metal ridge l5 so asto expel excess pitch through the four notches II, the parts being heldin this position until the pitch cooled and hardened.- This prior methodnot only resulted in waste of considerable pitch, but also producedinsecure fastenings, and in accordance with my p present invention, Iadditionally provide each mounting block I with an eccentric opening 2|and with an annular indentation 22 disposed within its recess l5directly beneath the inner edges of the radial notches l1 thereof. Ialso provide a number of block embracing rings 22 formed of suitablemetal and each having a central bore 24 adapted to quite snugly receivethe blocks l4, each ring 23 being provided with an inwardly extendinglower flange 25 and with an upper overflow notch 26 and being bounded bya side wall of slightly greater height than that of the blocks l4, sothat when a block I4 is positioned within a ring 23 and rests upon theflange 25 and a lense blank 9 is placed in contact with the upper ringedge as in Fig. 3, the blank will not contact the ridge 18 but willremain spaced slightly therefrom.

When utilizing my improved apparatus for attaching a standard lens blank8 to a mounting block [4, I first oil or grease the bore 24 of one ofthe ring 23 and after setting the ring on a support, I drop a block llin preheated condition within the bore 24 and against the lower flange25 with one of the block notches H in alinement with the overflow notch26 of the supporting ring 23, the other three notches l1 however beingsealed externally by the ring bore 24. I thereafter deposit a preheateddry lens blank 9 upon the upper edge of the ring 23 with the convexsurface H] of the blank facing the recess l5 and the peripheral portionof this lower blank surface resting upon the upper ring edge but spacedfrom the ridge l1 and annular indentation of the block I! as shown inFig. 3. After the hair lines i2 on the upper concave surface II of theblank 9 have been brought into proper and exact alinement with the fournotches ll of the mounting block l4 the blank 9 should be firmly pressedagainst the top edge of the ring 23, and while pressure is thus applied,hot molten pitch 20 should be gradually injected into the recess l-5through the block opening 2|.

This pitch injection should be slowly and carefully accomplished so asto permit all air to escape from wthin the cavity or rec'ess l5 throughthe alned notches I1, 26 of the block I and ring 23 respectively, andshould also be continued until the entire recess [5 including theindentation 22 and the annular space between the top of the ridge l6 andthe adjacent peripheral portion of the surface l0 hasbeen completelyfilled with pitch 20 only, and the pitch becomes visible at the ringnotch 26. The pitch injection may then be discontinued but the injectionpressure and the downward pressure on the lens blank 8 should bemaintained until after the injected pitch 20 has cooled and hardened,whereupon the attachment is complete and the blank 9 will be firmlysecured to-the block I 4 through a pitch bed alone and withoutcontacting the block directly. The block H with the blank firmlyattached thereto may then be withdrawn from the ring bore 24. fortransfer to the lens grinder and polisher. In this manner the successiveblanks 9 may be quickly and effectively secured to mounting blocks l4with pitch applied throughout the entire surfaces ill of the blanks, andwithout wasting any pitch 20 whatsoever, and after the lenses have beenground and polished, they may be quickly released from the pitch bymerely immersing the assemblages in cold water or the like.

In order to facilitate rapid and-convenient exploitation of my improvedmode of attachment, I have also provided improved apparatus formaintaining the pitch 20 in properly heated and fiuent condition, forholding the successive block and ring assemblages in proper position andfor clamping the lens blanks 9 thereto, and for in- Jecting the moltenpitch 20 into the recesses l of the successive assemblages. Asillustrated in the drawing, a preferred form of the improved apparatuscomprises in general, a cup-shaped pitch confining receptacle 21 havinga bottom 23 subjected to heat by an ordinary electric disk heater 29; anagitator 30 confined centrally within the receptacle 21 and beingoperable by a crank 3| secured to its carrying shaft 32; a support 33for the block and ring assemblages having a bar 34 and a pin 35 thereonengageable with the successive ring flanges 25 to maintain the rings 23in horizontal position; a lens blank holding arm 31 pivotally secured toan upright stem 38 having a pitch inlet and shut-off valve 39 associatedwith the lower end thereof, the arm 31 being provided with a lens blankcontacting projection 40; and a manually bperable pump having a cylinder4| which may be provided with a passage 42 immersed within the pitch 20and also having a pitch supply and outlet pipe 43 communicable past thevalve 39 with the interior of thereceptacle 21 and with the openings 2|of the successive mounting blocks l4 carried by the bar 34 and pin 35,the pump cylinder 4| also having therein a plunger 44 operable by alever 45.

The cup-shaped receptacle 21 may be insulated in any suitable manner andin order to produce a complete portable unit, this receptacle may beprovided with a built-in thermometer 41 for indicating the temperatureof the pitch 20, and with a control switch 43 for the electric heater29, at the front of the assemblage as shown in Fig. 1. The front wall ofthe receptacle 21 may also be provided with an upwardly projectingknock-out 49 for removing the assembled mounting blocks l4 and lensblanks 9 from the successive rings 23; and a hand rest 50 forfacilitating accurate positioning of the blanks 9 upon the rings 23while resting upon the supports 34, 35,

is provided at the upper side portion of the receptacle 21. The electricheater may be connected to a suitable source of electricity by means ofdetachable conductors 5i, and is concealed within a lower pocket of thereceptacle 23 directly beneath the'bottom 28, and the pitch agitator 30is of the vaned or propeller type and is preferably disposed directlyabove the bottom 28 beneath the pitch injection pump. The agitatorsupporting shaft 32 is journalled for rotation within the upper support33 and the latter provides a closure for the major portion of the pitchreceptacle but is provided with a pitch supply and removal opening 52.

The upper support 33 is firmly attached to the receptacle 21, andbesides carrying the bar 34 and pin 35 upon which the successive rings23 are mountable in truly horizontal position, the support 33 alsoconstitutes a guide for the upright stem 38 which pivotally supports thearm 31 and which has the shut-oil valve 39 associated with its lowerend. The end of the arm 31 remote from the pivot stem 38 is providedwith a manipulating handle 53, and this arm 31 may be swung about thestem axis from lens blank clamping or active position as shown in Figs.1

and 2, to release or inactive position against a stop pin 54 carried bythe receptacle, and is also adapted to be swung vertically about itssuspension pivot 55. A compression spring 53 is interposed between theoverhanging end of the arm 31 nearest the stem 38, and a lug 51 carriedby the pivot stem, as shown in Fig. 6. and this spring constantly tendsto swing the clamping projection 40 of the arm 31 downwardly.

The lower portion of the pivot stem 38 and with which the shut-off valve33 is associated, is snugly but rotatably confined within the uprightbore of a fixed casing 59 having aiined ports 30 communicating with theadjacent sections of the pump discharge pipe 43, and also having a transverse port 8| communicable with the pitch basin past a strainer 62, seeFigs. 2 and "I. The outlet end of the pipe 43 is provided with a fitting83 for attaching the pipe to the support 33, and a nozzle 64 carried bythe support 33 is in open communication at its lower end with thefitting 63 while its upper end projects considerably above the support33 and is adapted to be snugly slip-fitted into the openin s 2| of thesuccessive mounting blocks 14. When the clamping arm 39 is in activeposition as in Figs. 1 and 2, the valve 39 is in the position shown inFig. 7 with the pump displacement chamber in open communication with thepitch delivery nozzle 64; but when the arm 31 is swung in acounter-clockwise direction as viewed in Fig. 1 until it engages thefixed stop pin 54, the valve 39 will be shifted so as to connect thepump displacement chamber with the interior of the reservoir 21 throughthe port BI and past the strainer 62, and the nozzle 64 will be cut-offfrom communication with the pump.

The pump cylinder 4| is firmly connected to the reservoir 21 with itsbore disposed vertically, and the passage 42 is not essential and may beomitted, but may aid in permitting more rapid escape of air duringinitial conditioning of the unit for normal use. The medial portion ofthe pump actuating lever 45 is pivotally attached to the upper end ofthe plunger 44, while one end of this lever is fulcrumed on a bracketBS-carried by the receptacle 21 and the other end is provided with amanipulating handle 65. The lever 45 is also engaged by a helicalcompression spring 61 coacting therewith and with a-fixed closure plate68 for the pitch receptacle 21, be-

tween the handle 66 and the plunger 44, and this spring 61 tends toconstantly move the pump plunger 44 into uppermost position as shown inFig. 2. An elongated arcuate guide pin 63 which is swingably suspendedfrom another bracket 10' carried by the receptacle 21, coacts with anopening formed in the swinging end of the lever 45 as illustrated inFigs. 1 and 5, and the handle 66 is n screw threaded into the lever endand has a central pin 12 which is cooperable with the guide pin 69 tolock the lever 45 and pump plunger 44 in any desired vertical position.The handle 66 may also be provided with a transverse pin 13 co operablewith a stop pin 14 carried by the lever 45 when the handle 66 isrotated, in order to prevent complete release or removal of the handlefrom the lever during normal use.

Although the use of the improved apparatus while carrying on my improvedlens blank blocking system should be apparent from the detaileddescription of the blocking unit, the normal operation is as follows.The receptacle 21 should be supplied through the opening 52 with anabundance of pitch 20 which when melted extends approximately up to thelevel shown, and this pitch should be heated with the aid of the heater29 and as indicated by the thermometer 41, to a temperature sufllcientto thoroughly melt the same. The molten pitchshould be well stirred withthe aid of the agitator 30 and all air should be expelled from the pumpdisplacement chamber, the outlet pipe 43, valve 39, stringer 62, fitting63 and nipple 64, by reciprocating the plunger 44 several times, so thatall of the spaces communicating with the pump will be filled withair-free molten pitch. The successive pre-heated and moisture freemounting block I4 and ring 23 assemblages may then be placed upon thefixed supporting bar 39 and pin 35 with the pitch filled nozzle 69slip-fitted into the block opening 2|, whereupon the lens blanks 9 maybe deposited upon the upper ring edges and manually clamped in placewith the clamping arm 31. The pump plunger 44 may then be released andcarefully manipulated with the aid of the lever 45 to gradually injectpitch 20 under pressure through the pipe 43, valve 39, fitting 63 andnozzle 64 into the recesses l5 of the successive mounting block, ringand lens blank assemblages, and this injection of pitch should in eachcase be continued only until pitch is visible at the alined notches ll,26 of the block 14 and ring 23, respectively.

The injected pitch will then fill the recess l5 and the space betweenthe block ridge i6 and the adjacent lower convex surface I ll of theblank 9 and will extend completely across the top of the block it sothat no direct contact remains between the block I I and the blank 9.After each pitch injection, the arm 31 should be retained in clampingposition and the pump plunger 44 should be locked in lowered position bytwisting the handle 66 of .the actuating lever 45, until after the pitch20 within the recess l5 has set or hardened. The clamping arm 31 maythereafter be lifted and swung rearwardly against the stop pin 54, thusactuating the valve 39,.and positively cutting-oil communication betweenthe pump and the nozzle 64 but maintaining the conduits beyond the valve39 filled with pitch, and the pump lever locking pin 12 may also bereleased to permit the spring 61 to raise the plunger 44 and to draw afresh batch of pitch into the cylinder ll past the strainer 62. Thecompleted ring, block and lens blank assemblage may then be removed andthe knock-out 49 may be employed to displace the mounting block H fromthe ring 23, whereupon the lens blank 9 will be firmly attached to theblock I4 preparatory to grinding and polishing. The successive blanks 9may thus be most efiectively blocked, and by actuating the valve 39 withthe aid of the clamping arm 31 and by also locking the pump plunger 44in lowered position after each pitch injection, successive air-freepitch attachments are assured.

From the foregoing detailed description, it will be apparent that mypresent invention provides a highly effective system of blocking lensblanks with the aid of molten pitch, and also provides simple andreadily manipulable apparatus for carrying on the improved mode of lensblocking in a safe and expeditious manner. The lens mounts resultingfrom the use of the improved apparatus are free from air bubbles andfrom metal to glass contact. and the attaching pitch beds also extendthroughout maximum available area between the mounting blocks and lensblanks, thus insuring firm attachment and minimizing the danger ofhaving the blanks 9 becoming detached during the subsequent grinding andpolishing operations. The improvement may also be safely andconveniently exploited with the improved portable unit, and waste ofpitch is entirely eliminated. The annular notch 22 enhances the holdingeffect and the improved apparatus is flexible in its adaptations formounting diflerent types of lenses, and has proven highly satisfactoryand successful in actual commercial use, especially in the manufactureof more perfect optical lenses.

It should be understood that it is not desired to limit this inventionto the precise details of construction of the apparatus, herein shownand described, for' various modifications within the scope of theappended claims may occur to persons skilled in the art; and it is alsocontemplated that specific descriptive terms employed herein be giventhe broadest possible interpretation consistent with the disclosure.

I claim:

1. Apparatus for fastening a lens blank to a mounting block having arecess for the reception of attaching pitch, which comprises, an annularwall formed to snugly receive a lens mounting block and to provide asubstantially continuous rim extending a slight distance upwardly beyondthe peripheral edge of the block recess, means for supporting said walland the block therein with said rim projecting above the peripheral edgeof the block recess to provide a continuous annular lens blank supportspaced from the block, and means for injecting fluent pitch upwardlythrough the lowest portion of the bottom of the recess to fill the spacebetween the blank and the block within said wall 2. Apparatus forfastening a lens blank to a recessed mounting black with the aid ofpitch,

which comprises, a fluent pitch receptacle, a lens blank mounting blocksupport, an arm for clamping a lens blank relative to a block restingupon said support, a pump for injecting fluent pitch from saidreceptacle into the space between said block and said lens blank, and ashut-off valve for cutting off the connection from said pump to saidspace when said arm is removed from clamping position.

3. Apparatus for fastening a lens blank to a recessed mounting blockwith the aid of pitch, which comprises, a fluent pitch receptacle, alens blank mounting block support, an arm for clamping a lens blankrelative to a block resting upon said support, a pump for injectingfluent pitch from said receptacle upwardly through said block into thespace between said block and said lens blank, and a shut-off valve forcutting off communication between said pump and said space and forconnecting the displacement chamber of the pump with the interior ofsaid receptacle when said arm is swung laterally away from lens clampingposition.

4. Apparatus for fastening a lens blank to-a recessed mounting blockwith the aid of pitch, which comprises, a fluent pitch receptacle, alens blank mounting block support, a pump having a plunger forinjectingfluent pitch from said receptacle into the space between saidblock and a lens disposed thereabove, a lever for actuating the pumpplunger, a handle for manipulating said lever, and means operable bysaid handle for lock- 9 ing said lever and said plunger in variouspositions.

5. Apparatus for fastening a lens blank to a recessed mounting blockwith the aid of pitch, which comprises, a fluent pitch receptacle, asupport for a lens blank mounting block, an arm for clamping a lensblank relative to a block resting upon said support, said arm beingswingable vertically to eflect clampingaction and being horizontallyremovable from clamping position, a pump for injecting pitch from saidreceptacle into the recess of said mounting block, and means operable bythe horizontal motion of said arm for shutting ofi the supply of pitchfrom said pump to said recess.

6. Apparatus for fastening a lens blank to a recessed mounting blockwith the aid of pitch, which comprises, a fluent pitch receptacle, asupport for a lens blank mounting'block, an arm for clamping a lensblank relative to a block resting upon said support, said arm beingswingable vertically to efiect clamping action and being horizontallyremovable from. clamping position, a pump for injecting pitch from saidreceptacle into the recess of said mounting block, means operable by thehorizontal motion of said arm for shutting off the supply of pitch fromsaid pump to said recess, and means for locking the displacement plungerof said pump against movement.

7. Apparatus for fastening a lens blank to a recessed mounting blockwith the aid of pitch,

which comprises, a fluent pitch receptacle, a

said pitch injecting means to said space when said lens clamping meansis removed from clamping 15 position.

FRED G. FRITZSCHE.

.REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date McCabe Aug. 16, 1932 Challet Apr. 9,1918 Number McCabe Feb. 18, 1936

